Modeling temperature distribution upon liquid-nitrogen injection into a self heating coal mine goaf

• Published in: Process safety and environmental protection Vol. 126; pp. 278 - 286
• Main Authors: Shi, Guo-Qing, Ding, Peng-xiang, Guo, Zhixiong, Wang, Yan-ming
• Format: Journal Article
• Language: English
• Published: Rugby Elsevier B.V 01.06.2019; Elsevier Science Ltd
• Subjects: Ceramics industry; Coal; Coal mines; Coal mining; Coal spontaneous combustion; Combustion; Computer simulation; Cooling; Cooling rate; Field tests; Flow rates; Flow velocity; Goaf; Injection; Liquid nitrogen; Low temperature; Mathematical models; Numerical simulation; Oxidation; Perfusion; Production planning; Self heating; Spontaneous combustion; Temperature distribution; Temperature effects; Temperature distribution; Numerical simulation; Goaf; Liquid nitrogen; Coal spontaneous combustion
• ISSN: 0957-5820; 1744-3598
• DOI: 10.1016/j.psep.2019.03.033

•Both field test and simulation show occurrence of coal oxidation in workface #3418.•Injection of liquid N2 forms a cooling zone suppressing coal oxidation.•Injection of N2 reduces maximum goaf temperature preventing spontaneous combustion.•Cooling zone and effectiveness are strongly affected by injection location and rate. Liquid N2 could be injected into goaf to decrease temperature and prevent spontaneous combustion during mining. A working face at Liangbaosi coal mine was adopted for study. Firstly, a mathematical model for calculating the temperature field in goaf was developed and field tests without injection of liquid N2 were conducted to validate the model. Comparable development trends and hot zones between the simulation and field measurements were found. The hot zones were located about 35–45 m behind the workface on the air-return and air-intake sides in the goaf. Then the model was employed to simulate the time development of temperature distribution in the goaf with injection of liquid N2 from different locations. It was observed that a low-temperature cooling zone (<300K) due to injection of liquid N2 gradually grew and became relatively stable 90 min after continuous injection. The size of the cooling zone depends on the injection location and flow rate. The cooling zone was smaller when the N2 was injected from the air-intake side than from the air-return side. The largest cooling zone was found when the N2 was injected 35m behind the workface from the air-return side. The cooling zone increases with increasing N2 perfusion rate. This study provides a quantitative assessment for preventing coal oxidation and spontaneous combustion using the liquid N2 technology.